Herein, a transmission in particular designates a multi-speed transmission, with which a multitude of gears, thus transmission ratio relationships between the drive shaft and the output shaft, are shiftable by shift elements, preferably automatically. Herein, the shift elements comprise, for example, clutches or brakes. Such transmissions are primarily used in automotive applications, in order to adjust the rotational speed and torque output characteristics of the drive unit to the driving resistance of the vehicle in a suitable manner.
Patent application DE 10 2013 223 427 A1 of the applicant describes a power-shifting transmission for a hybrid drive train, comprising an upstream gear set and a main gear set, each of which consists of two dual planetary gear sets that are coupled with each other. The upstream gear set is configured to make available two rotational speeds that are reduced compared to the rotational speed of the transmission input shaft. Thereby, the rotor of the electric motor is constantly connected to the shaft of the main gear set that is first in the order of rotational speeds.
Patent application DE 10 2013 223 426 A1 of the applicant describes a transmission for a hybrid drive train, comprising an upstream gear set and a main gear set, each of which consists of two dual planetary gear sets that are coupled with each other. The upstream gear set is configured to make available a rotational speed that is increased compared to the rotational speed of the transmission input shaft and a rotational speed that is reduced compared to the rotational speed of the transmission input shaft. Thereby, the rotor of the electric motor is constantly connected to the shaft of the main gear set that is first in the order of rotational speeds.
In both known transmissions, the rotor of the electric motor is attached to the shaft of the main gear set that is first in the order of rotational speeds. In the rotational speed diagrams shown in FIG. 1 of the aforementioned patent applications, it is clearly recognizable that the rotational speed of the first shaft of the main gear set regularly takes on only low rotational speeds, or is even fixed in a torque-proof manner. If this first shaft is fixed in a torque-proof manner, it is not able to deliver or absorb any torque. With a low rotational speed of such first shaft, the electric motor must have such correspondingly large dimensions to be able to deliver the torque necessary for the target power. This is undesirable, because, in driving mode, the electric motor should be available wherever possible in any gear to deliver and absorb power; for example, for recuperation. Thereby, the electric motor should feature dimensions that are as small as possible.